Pull parisc architecture fixes from Helge Deller:
"Fix an unaligned-access crash in the bootloader and drop asm/swab.h"
* tag 'for-5.15/parisc-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
parisc: Fix unaligned-access crash in bootloader
parisc: Drop __arch_swab16(), arch_swab24(), _arch_swab32() and __arch_swab64() functions
Pull MIPS updates from Thomas Bogendoerfer:
- converted Pistachio platform to use MIPS generic kernel
- fixes and cleanups
* tag 'mips_5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (29 commits)
MIPS: Malta: fix alignment of the devicetree buffer
MIPS: ingenic: Unconditionally enable clock of CPU #0
MIPS: mscc: ocelot: mark the phy-mode for internal PHY ports
MIPS: mscc: ocelot: disable all switch ports by default
MAINTAINERS: adjust PISTACHIO SOC SUPPORT after its retirement
MIPS: Return true/false (not 1/0) from bool functions
MIPS: generic: Return true/false (not 1/0) from bool functions
MIPS: Make a alias for pistachio_defconfig
MIPS: Retire MACH_PISTACHIO
MIPS: config: generic: Add config for Marduk board
pinctrl: pistachio: Make it as an option
phy: pistachio-usb: Depend on MIPS || COMPILE_TEST
clocksource/drivers/pistachio: Make it selectable for MIPS
clk: pistachio: Make it selectable for generic MIPS kernel
MIPS: DTS: Pistachio add missing cpc and cdmm
MIPS: generic: Allow generating FIT image for Marduk board
MIPS: locking/atomic: Fix atomic{_64,}_sub_if_positive
MIPS: loongson2ef: don't build serial.o unconditionally
MIPS: Replace deprecated CPU-hotplug functions.
MIPS: Alchemy: Fix spelling contraction "cant" -> "can't"
...
Pull OpenRISC updates from Stafford Horne:
"A few cleanups and compiler warning fixes for OpenRISC.
Also, this includes dts and defconfig updates to enable Ethernet on
OpenRISC/Litex FPGA SoC's now that the LiteEth driver has gone
upstream"
* tag 'for-linus' of git://github.com/openrisc/linux:
openrisc/litex: Update defconfig
openrisc/litex: Add ethernet device
openrisc/litex: Update uart address
openrisc: Fix compiler warnings in setup
openrisc: rename or32 code & comments to or1k
openrisc: don't printk() unconditionally
Pull livepatching update from Petr Mladek.
* tag 'livepatching-for-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
livepatch: Replace deprecated CPU-hotplug functions.
Pull iommu updates from Joerg Roedel:
- New DART IOMMU driver for Apple Silicon M1 chips
- Optimizations for iommu_[map/unmap] performance
- Selective TLB flush support for the AMD IOMMU driver to make it more
efficient on emulated IOMMUs
- Rework IOVA setup and default domain type setting to move more code
out of IOMMU drivers and to support runtime switching between certain
types of default domains
- VT-d Updates from Lu Baolu:
- Update the virtual command related registers
- Enable Intel IOMMU scalable mode by default
- Preset A/D bits for user space DMA usage
- Allow devices to have more than 32 outstanding PRs
- Various cleanups
- ARM SMMU Updates from Will Deacon:
SMMUv3:
- Minor optimisation to avoid zeroing struct members on CMD submission
- Increased use of batched commands to reduce submission latency
- Refactoring in preparation for ECMDQ support
SMMUv2:
- Fix races when probing devices with identical StreamIDs
- Optimise walk cache flushing for Qualcomm implementations
- Allow deep sleep states for some Qualcomm SoCs with shared clocks
- Various smaller optimizations, cleanups, and fixes
* tag 'iommu-updates-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu: (85 commits)
iommu/io-pgtable: Abstract iommu_iotlb_gather access
iommu/arm-smmu: Fix missing unlock on error in arm_smmu_device_group()
iommu/vt-d: Add present bit check in pasid entry setup helpers
iommu/vt-d: Use pasid_pte_is_present() helper function
iommu/vt-d: Drop the kernel doc annotation
iommu/vt-d: Allow devices to have more than 32 outstanding PRs
iommu/vt-d: Preset A/D bits for user space DMA usage
iommu/vt-d: Enable Intel IOMMU scalable mode by default
iommu/vt-d: Refactor Kconfig a bit
iommu/vt-d: Remove unnecessary oom message
iommu/vt-d: Update the virtual command related registers
iommu: Allow enabling non-strict mode dynamically
iommu: Merge strictness and domain type configs
iommu: Only log strictness for DMA domains
iommu: Expose DMA domain strictness via sysfs
iommu: Express DMA strictness via the domain type
iommu/vt-d: Prepare for multiple DMA domain types
iommu/arm-smmu: Prepare for multiple DMA domain types
iommu/amd: Prepare for multiple DMA domain types
iommu: Introduce explicit type for non-strict DMA domains
...
When the NFS server receives a large gss (kerberos) credential and tries
to pass it up to rpc.svcgssd (which is deprecated), it triggers an
infinite loop in cache_read().
cache_request() always returns -EAGAIN, and this causes a "goto again".
This patch:
- changes the error to -E2BIG to avoid the infinite loop, and
- generates a WARN_ONCE when rsi_request first sees an over-sized
credential. The warning suggests switching to gssproxy.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=196583
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Pull swiotlb updates from Konrad Rzeszutek Wilk:
"A new feature called restricted DMA pools. It allows SWIOTLB to
utilize per-device (or per-platform) allocated memory pools instead of
using the global one.
The first big user of this is ARM Confidential Computing where the
memory for DMA operations can be set per platform"
* 'stable/for-linus-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb: (23 commits)
swiotlb: use depends on for DMA_RESTRICTED_POOL
of: restricted dma: Don't fail device probe on rmem init failure
of: Move of_dma_set_restricted_buffer() into device.c
powerpc/svm: Don't issue ultracalls if !mem_encrypt_active()
s390/pv: fix the forcing of the swiotlb
swiotlb: Free tbl memory in swiotlb_exit()
swiotlb: Emit diagnostic in swiotlb_exit()
swiotlb: Convert io_default_tlb_mem to static allocation
of: Return success from of_dma_set_restricted_buffer() when !OF_ADDRESS
swiotlb: add overflow checks to swiotlb_bounce
swiotlb: fix implicit debugfs declarations
of: Add plumbing for restricted DMA pool
dt-bindings: of: Add restricted DMA pool
swiotlb: Add restricted DMA pool initialization
swiotlb: Add restricted DMA alloc/free support
swiotlb: Refactor swiotlb_tbl_unmap_single
swiotlb: Move alloc_size to swiotlb_find_slots
swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing
swiotlb: Update is_swiotlb_active to add a struct device argument
swiotlb: Update is_swiotlb_buffer to add a struct device argument
...
Merge misc updates from Andrew Morton:
"173 patches.
Subsystems affected by this series: ia64, ocfs2, block, and mm (debug,
pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap,
bootmem, sparsemem, vmalloc, kasan, pagealloc, memory-failure,
hugetlb, userfaultfd, vmscan, compaction, mempolicy, memblock,
oom-kill, migration, ksm, percpu, vmstat, and madvise)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (173 commits)
mm/madvise: add MADV_WILLNEED to process_madvise()
mm/vmstat: remove unneeded return value
mm/vmstat: simplify the array size calculation
mm/vmstat: correct some wrong comments
mm/percpu,c: remove obsolete comments of pcpu_chunk_populated()
selftests: vm: add COW time test for KSM pages
selftests: vm: add KSM merging time test
mm: KSM: fix data type
selftests: vm: add KSM merging across nodes test
selftests: vm: add KSM zero page merging test
selftests: vm: add KSM unmerge test
selftests: vm: add KSM merge test
mm/migrate: correct kernel-doc notation
mm: wire up syscall process_mrelease
mm: introduce process_mrelease system call
memblock: make memblock_find_in_range method private
mm/mempolicy.c: use in_task() in mempolicy_slab_node()
mm/mempolicy: unify the create() func for bind/interleave/prefer-many policies
mm/mempolicy: advertise new MPOL_PREFERRED_MANY
mm/hugetlb: add support for mempolicy MPOL_PREFERRED_MANY
...
There is a usecase in Android that an app process's memory is swapped out
by process_madvise() with MADV_PAGEOUT, such as the memory is swapped to
zram or a backing device. When the process is scheduled to running, like
switch to foreground, multiple page faults may cause the app dropped
frames.
To reduce the problem, System Management Software can read-ahead memory
of the process immediately when the app switches to forground. Calling
process_madvise() with MADV_WILLNEED can meet this need.
Link: https://lkml.kernel.org/r/20210804082010.12482-1-zhangkui@oppo.com
Signed-off-by: zhangkui <zhangkui@oppo.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since merged pages are copied every time they need to be modified, the
write access time is different between shared and non-shared pages. Add
ksm_cow_time() function which evaluates latency of these COW breaks.
First, 4000 pages are allocated and the time, required to modify 1 byte in
every other page, is measured. After this, the pages are merged into 2000
pairs and in each pair, 1 page is modified (i.e. they are decoupled) to
detect COW breaks. The time needed to break COW of merged pages is then
compared with performance of non-shared pages.
The test is run as follows: ./ksm_tests -C
The output:
Total size: 15 MiB
Not merged pages:
Total time: 0.002185489 s
Average speed: 3202.945 MiB/s
Merged pages:
Total time: 0.004386872 s
Average speed: 1595.670 MiB/s
Link: https://lkml.kernel.org/r/1d03ee0d1b341959d4b61672c6401d498bff5652.1629386192.git.zhansayabagdaulet@gmail.com
Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@gmail.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In modern systems it's not unusual to have a system component monitoring
memory conditions of the system and tasked with keeping system memory
pressure under control. One way to accomplish that is to kill
non-essential processes to free up memory for more important ones.
Examples of this are Facebook's OOM killer daemon called oomd and
Android's low memory killer daemon called lmkd.
For such system component it's important to be able to free memory quickly
and efficiently. Unfortunately the time process takes to free up its
memory after receiving a SIGKILL might vary based on the state of the
process (uninterruptible sleep), size and OPP level of the core the
process is running. A mechanism to free resources of the target process
in a more predictable way would improve system's ability to control its
memory pressure.
Introduce process_mrelease system call that releases memory of a dying
process from the context of the caller. This way the memory is freed in a
more controllable way with CPU affinity and priority of the caller. The
workload of freeing the memory will also be charged to the caller. The
operation is allowed only on a dying process.
After previous discussions [1, 2, 3] the decision was made [4] to
introduce a dedicated system call to cover this use case.
The API is as follows,
int process_mrelease(int pidfd, unsigned int flags);
DESCRIPTION
The process_mrelease() system call is used to free the memory of
an exiting process.
The pidfd selects the process referred to by the PID file
descriptor.
(See pidfd_open(2) for further information)
The flags argument is reserved for future use; currently, this
argument must be specified as 0.
RETURN VALUE
On success, process_mrelease() returns 0. On error, -1 is
returned and errno is set to indicate the error.
ERRORS
EBADF pidfd is not a valid PID file descriptor.
EAGAIN Failed to release part of the address space.
EINTR The call was interrupted by a signal; see signal(7).
EINVAL flags is not 0.
EINVAL The memory of the task cannot be released because the
process is not exiting, the address space is shared
with another live process or there is a core dump in
progress.
ENOSYS This system call is not supported, for example, without
MMU support built into Linux.
ESRCH The target process does not exist (i.e., it has terminated
and been waited on).
[1] https://lore.kernel.org/lkml/20190411014353.113252-3-surenb@google.com/
[2] https://lore.kernel.org/linux-api/20201113173448.1863419-1-surenb@google.com/
[3] https://lore.kernel.org/linux-api/20201124053943.1684874-3-surenb@google.com/
[4] https://lore.kernel.org/linux-api/20201223075712.GA4719@lst.de/
Link: https://lkml.kernel.org/r/20210809185259.405936-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jan Engelhardt <jengelh@inai.de>
Cc: Tim Murray <timmurray@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are a lot of uses of memblock_find_in_range() along with
memblock_reserve() from the times memblock allocation APIs did not exist.
memblock_find_in_range() is the very core of memblock allocations, so any
future changes to its internal behaviour would mandate updates of all the
users outside memblock.
Replace the calls to memblock_find_in_range() with an equivalent calls to
memblock_phys_alloc() and memblock_phys_alloc_range() and make
memblock_find_in_range() private method of memblock.
This simplifies the callers, ensures that (unlikely) errors in
memblock_reserve() are handled and improves maintainability of
memblock_find_in_range().
Link: https://lkml.kernel.org/r/20210816122622.30279-1-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> [arm64]
Acked-by: Kirill A. Shutemov <kirill.shtuemov@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> [ACPI]
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Nick Kossifidis <mick@ics.forth.gr> [riscv]
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Introduce multi-preference mempolicy", v7.
This patch series introduces the concept of the MPOL_PREFERRED_MANY
mempolicy. This mempolicy mode can be used with either the
set_mempolicy(2) or mbind(2) interfaces. Like the MPOL_PREFERRED
interface, it allows an application to set a preference for nodes which
will fulfil memory allocation requests. Unlike the MPOL_PREFERRED mode,
it takes a set of nodes. Like the MPOL_BIND interface, it works over a
set of nodes. Unlike MPOL_BIND, it will not cause a SIGSEGV or invoke the
OOM killer if those preferred nodes are not available.
Along with these patches are patches for libnuma, numactl, numademo, and
memhog. They still need some polish, but can be found here:
https://gitlab.com/bwidawsk/numactl/-/tree/prefer-many It allows new
usage: `numactl -P 0,3,4`
The goal of the new mode is to enable some use-cases when using tiered memory
usage models which I've lovingly named.
1a. The Hare - The interconnect is fast enough to meet bandwidth and
latency requirements allowing preference to be given to all nodes with
"fast" memory.
1b. The Indiscriminate Hare - An application knows it wants fast
memory (or perhaps slow memory), but doesn't care which node it runs
on. The application can prefer a set of nodes and then xpu bind to
the local node (cpu, accelerator, etc). This reverses the nodes are
chosen today where the kernel attempts to use local memory to the CPU
whenever possible. This will attempt to use the local accelerator to
the memory.
2. The Tortoise - The administrator (or the application itself) is
aware it only needs slow memory, and so can prefer that.
Much of this is almost achievable with the bind interface, but the bind
interface suffers from an inability to fallback to another set of nodes if
binding fails to all nodes in the nodemask.
Like MPOL_BIND a nodemask is given. Inherently this removes ordering from the
preference.
> /* Set first two nodes as preferred in an 8 node system. */
> const unsigned long nodes = 0x3
> set_mempolicy(MPOL_PREFER_MANY, &nodes, 8);
> /* Mimic interleave policy, but have fallback *.
> const unsigned long nodes = 0xaa
> set_mempolicy(MPOL_PREFER_MANY, &nodes, 8);
Some internal discussion took place around the interface. There are two
alternatives which we have discussed, plus one I stuck in:
1. Ordered list of nodes. Currently it's believed that the added
complexity is nod needed for expected usecases.
2. A flag for bind to allow falling back to other nodes. This
confuses the notion of binding and is less flexible than the current
solution.
3. Create flags or new modes that helps with some ordering. This
offers both a friendlier API as well as a solution for more customized
usage. It's unknown if it's worth the complexity to support this.
Here is sample code for how this might work:
> // Prefer specific nodes for some something wacky
> set_mempolicy(MPOL_PREFER_MANY, 0x17c, 1024);
>
> // Default
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_SOCKET, NULL, 0);
> // which is the same as
> set_mempolicy(MPOL_DEFAULT, NULL, 0);
>
> // The Hare
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_TYPE, NULL, 0);
>
> // The Tortoise
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_TYPE_REV, NULL, 0);
>
> // Prefer the fast memory of the first two sockets
> set_mempolicy(MPOL_PREFER_MANY | MPOL_F_PREFER_ORDER_TYPE, -1, 2);
>
This patch (of 5):
The NUMA APIs currently allow passing in a "preferred node" as a single
bit set in a nodemask. If more than one bit it set, bits after the first
are ignored.
This single node is generally OK for location-based NUMA where memory
being allocated will eventually be operated on by a single CPU. However,
in systems with multiple memory types, folks want to target a *type* of
memory instead of a location. For instance, someone might want some
high-bandwidth memory but do not care about the CPU next to which it is
allocated. Or, they want a cheap, high capacity allocation and want to
target all NUMA nodes which have persistent memory in volatile mode. In
both of these cases, the application wants to target a *set* of nodes, but
does not want strict MPOL_BIND behavior as that could lead to OOM killer
or SIGSEGV.
So add MPOL_PREFERRED_MANY policy to support the multiple preferred nodes
requirement. This is not a pie-in-the-sky dream for an API. This was a
response to a specific ask of more than one group at Intel. Specifically:
1. There are existing libraries that target memory types such as
https://github.com/memkind/memkind. These are known to suffer from
SIGSEGV's when memory is low on targeted memory "kinds" that span more
than one node. The MCDRAM on a Xeon Phi in "Cluster on Die" mode is an
example of this.
2. Volatile-use persistent memory users want to have a memory policy
which is targeted at either "cheap and slow" (PMEM) or "expensive and
fast" (DRAM). However, they do not want to experience allocation
failures when the targeted type is unavailable.
3. Allocate-then-run. Generally, we let the process scheduler decide
on which physical CPU to run a task. That location provides a default
allocation policy, and memory availability is not generally considered
when placing tasks. For situations where memory is valuable and
constrained, some users want to allocate memory first, *then* allocate
close compute resources to the allocation. This is the reverse of the
normal (CPU) model. Accelerators such as GPUs that operate on
core-mm-managed memory are interested in this model.
A check is added in sanitize_mpol_flags() to not permit 'prefer_many'
policy to be used for now, and will be removed in later patch after all
implementations for 'prefer_many' are ready, as suggested by Michal Hocko.
[mhocko@kernel.org: suggest to refine policy_node/policy_nodemask handling]
Link: https://lkml.kernel.org/r/1627970362-61305-1-git-send-email-feng.tang@intel.com
Link: https://lore.kernel.org/r/20200630212517.308045-4-ben.widawsky@intel.com
Link: https://lkml.kernel.org/r/1627970362-61305-2-git-send-email-feng.tang@intel.com
Co-developed-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Huang Ying <ying.huang@intel.com>b
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The proactive compaction[1] gets triggered for every 500msec and run
compaction on the node for COMPACTION_HPAGE_ORDER (usually order-9) pages
based on the value set to sysctl.compaction_proactiveness. Triggering the
compaction for every 500msec in search of COMPACTION_HPAGE_ORDER pages is
not needed for all applications, especially on the embedded system
usecases which may have few MB's of RAM. Enabling the proactive
compaction in its state will endup in running almost always on such
systems.
Other side, proactive compaction can still be very much useful for getting
a set of higher order pages in some controllable manner(controlled by
using the sysctl.compaction_proactiveness). So, on systems where enabling
the proactive compaction always may proove not required, can trigger the
same from user space on write to its sysctl interface. As an example, say
app launcher decide to launch the memory heavy application which can be
launched fast if it gets more higher order pages thus launcher can prepare
the system in advance by triggering the proactive compaction from
userspace.
This triggering of proactive compaction is done on a write to
sysctl.compaction_proactiveness by user.
[1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=facdaa917c4d5a376d09d25865f5a863f906234a
[akpm@linux-foundation.org: tweak vm.rst, per Mike]
Link: https://lkml.kernel.org/r/1627653207-12317-1-git-send-email-charante@codeaurora.org
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Nitin Gupta <nigupta@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drop_slab_node() is called as part of echo 2>/proc/sys/vm/drop_caches
operation. It iterates over all memcgs and calls shrink_slab() which in
turn iterates over all slab shrinkers. Freed objects are counted and as
long as the total number of freed objects from all memcgs and shrinkers is
higher than 10, drop_slab_node() loops for another full memcgs*shrinkers
iteration.
This arbitrary constant threshold of 10 can result in effectively an
infinite loop on a system with large number of memcgs and/or parallel
activity that allocates new objects. This has been reported previously by
Chunxin Zang [1] and recently by our customer.
The previous report [1] has resulted in commit 069c411de4 ("mm/vmscan:
fix infinite loop in drop_slab_node") which added a check for signals
allowing the user to terminate the command writing to drop_caches. At the
time it was also considered to make the threshold grow with each iteration
to guarantee termination, but such patch hasn't been formally proposed
yet.
This patch implements the dynamically growing threshold. At first
iteration it's enough to free one object to continue, and this threshold
effectively doubles with each iteration. Our customer's feedback was
positive.
There is always a risk that this change will result on some system in a
previously terminating drop_caches operation to terminate sooner and free
fewer objects. Ideally the semantics would guarantee freeing all freeable
objects that existed at the moment of starting the operation, while not
looping forever for newly allocated objects, but that's not feasible to
track. In the less ideal solution based on thresholds, arguably the
termination guarantee is more important than the exhaustiveness guarantee.
If there are reports of large regression wrt being exhaustive, we can
tune how fast the threshold grows.
[1] https://lore.kernel.org/lkml/20200909152047.27905-1-zangchunxin@bytedance.com/T/#u
[vbabka@suse.cz: avoid undefined shift behaviour]
Link: https://lkml.kernel.org/r/2f034e6f-a753-550a-f374-e4e23899d3d5@suse.cz
Link: https://lkml.kernel.org/r/20210818152239.25502-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Chunxin Zang <zangchunxin@bytedance.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some method is obviously needed to enable reclaim-based migration.
Just like traditional autonuma, there will be some workloads that will
benefit like workloads with more "static" configurations where hot pages
stay hot and cold pages stay cold. If pages come and go from the hot and
cold sets, the benefits of this approach will be more limited.
The benefits are truly workload-based and *not* hardware-based. We do not
believe that there is a viable threshold where certain hardware
configurations should have this mechanism enabled while others do not.
To be conservative, earlier work defaulted to disable reclaim- based
migration and did not include a mechanism to enable it. This proposes add
a new sysfs file
/sys/kernel/mm/numa/demotion_enabled
as a method to enable it.
We are open to any alternative that allows end users to enable this
mechanism or disable it if workload harm is detected (just like
traditional autonuma).
Once this is enabled page demotion may move data to a NUMA node that does
not fall into the cpuset of the allocating process. This could be
construed to violate the guarantees of cpusets. However, since this is an
opt-in mechanism, the assumption is that anyone enabling it is content to
relax the guarantees.
Link: https://lkml.kernel.org/r/20210721063926.3024591-9-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-10-ying.huang@intel.com
Signed-off-by: Huang Ying <ying.huang@intel.com>
Originally-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Migrate Pages in lieu of discard", v11.
We're starting to see systems with more and more kinds of memory such as
Intel's implementation of persistent memory.
Let's say you have a system with some DRAM and some persistent memory.
Today, once DRAM fills up, reclaim will start and some of the DRAM
contents will be thrown out. Allocations will, at some point, start
falling over to the slower persistent memory.
That has two nasty properties. First, the newer allocations can end up in
the slower persistent memory. Second, reclaimed data in DRAM are just
discarded even if there are gobs of space in persistent memory that could
be used.
This patchset implements a solution to these problems. At the end of the
reclaim process in shrink_page_list() just before the last page refcount
is dropped, the page is migrated to persistent memory instead of being
dropped.
While I've talked about a DRAM/PMEM pairing, this approach would function
in any environment where memory tiers exist.
This is not perfect. It "strands" pages in slower memory and never brings
them back to fast DRAM. Huang Ying has follow-on work which repurposes
NUMA balancing to promote hot pages back to DRAM.
This is also all based on an upstream mechanism that allows persistent
memory to be onlined and used as if it were volatile:
http://lkml.kernel.org/r/20190124231441.37A4A305@viggo.jf.intel.com
With that, the DRAM and PMEM in each socket will be represented as 2
separate NUMA nodes, with the CPUs sit in the DRAM node. So the
general inter-NUMA demotion mechanism introduced in the patchset can
migrate the cold DRAM pages to the PMEM node.
We have tested the patchset with the postgresql and pgbench. On a
2-socket server machine with DRAM and PMEM, the kernel with the patchset
can improve the score of pgbench up to 22.1% compared with that of the
DRAM only + disk case. This comes from the reduced disk read throughput
(which reduces up to 70.8%).
== Open Issues ==
* Memory policies and cpusets that, for instance, restrict allocations
to DRAM can be demoted to PMEM whenever they opt in to this
new mechanism. A cgroup-level API to opt-in or opt-out of
these migrations will likely be required as a follow-on.
* Could be more aggressive about where anon LRU scanning occurs
since it no longer necessarily involves I/O. get_scan_count()
for instance says: "If we have no swap space, do not bother
scanning anon pages"
This patch (of 9):
Prepare for the kernel to auto-migrate pages to other memory nodes with a
node migration table. This allows creating single migration target for
each NUMA node to enable the kernel to do NUMA page migrations instead of
simply discarding colder pages. A node with no target is a "terminal
node", so reclaim acts normally there. The migration target does not
fundamentally _need_ to be a single node, but this implementation starts
there to limit complexity.
When memory fills up on a node, memory contents can be automatically
migrated to another node. The biggest problems are knowing when to
migrate and to where the migration should be targeted.
The most straightforward way to generate the "to where" list would be to
follow the page allocator fallback lists. Those lists already tell us if
memory is full where to look next. It would also be logical to move
memory in that order.
But, the allocator fallback lists have a fatal flaw: most nodes appear in
all the lists. This would potentially lead to migration cycles (A->B,
B->A, A->B, ...).
Instead of using the allocator fallback lists directly, keep a separate
node migration ordering. But, reuse the same data used to generate page
allocator fallback in the first place: find_next_best_node().
This means that the firmware data used to populate node distances
essentially dictates the ordering for now. It should also be
architecture-neutral since all NUMA architectures have a working
find_next_best_node().
RCU is used to allow lock-less read of node_demotion[] and prevent
demotion cycles been observed. If multiple reads of node_demotion[] are
performed, a single rcu_read_lock() must be held over all reads to ensure
no cycles are observed. Details are as follows.
=== What does RCU provide? ===
Imagine a simple loop which walks down the demotion path looking
for the last node:
terminal_node = start_node;
while (node_demotion[terminal_node] != NUMA_NO_NODE) {
terminal_node = node_demotion[terminal_node];
}
The initial values are:
node_demotion[0] = 1;
node_demotion[1] = NUMA_NO_NODE;
and are updated to:
node_demotion[0] = NUMA_NO_NODE;
node_demotion[1] = 0;
What guarantees that the cycle is not observed:
node_demotion[0] = 1;
node_demotion[1] = 0;
and would loop forever?
With RCU, a rcu_read_lock/unlock() can be placed around the loop. Since
the write side does a synchronize_rcu(), the loop that observed the old
contents is known to be complete before the synchronize_rcu() has
completed.
RCU, combined with disable_all_migrate_targets(), ensures that the old
migration state is not visible by the time __set_migration_target_nodes()
is called.
=== What does READ_ONCE() provide? ===
READ_ONCE() forbids the compiler from merging or reordering successive
reads of node_demotion[]. This ensures that any updates are *eventually*
observed.
Consider the above loop again. The compiler could theoretically read the
entirety of node_demotion[] into local storage (registers) and never go
back to memory, and *permanently* observe bad values for node_demotion[].
Note: RCU does not provide any universal compiler-ordering
guarantees:
https://lore.kernel.org/lkml/20150921204327.GH4029@linux.vnet.ibm.com/
This code is unused for now. It will be called later in the
series.
Link: https://lkml.kernel.org/r/20210721063926.3024591-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20210715055145.195411-2-ying.huang@intel.com
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Xu <weixugc@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When userfaultfd copy-ioctl fails since the PTE already exists, an -EEXIST
error is returned and the faulting thread is not woken. The current
userfaultfd test does not wake the faulting thread in such case. The
assumption is presumably that another thread set the PTE through copy/wp
ioctl and would wake the faulting thread or that alternatively the fault
handler would realize there is no need to "must_wait" and continue. This
is not necessarily true.
There is an assumption that the "must_wait" tests in handle_userfault()
are sufficient to provide definitive answer whether the offending PTE is
populated or not. However, userfaultfd_must_wait() test is lockless.
Consequently, concurrent calls to ptep_modify_prot_start(), for instance,
can clear the PTE and can cause userfaultfd_must_wait() to wrongly assume
it is not populated and a wait is needed.
There are therefore 3 options:
(1) Change the tests to wake on copy failure.
(2) Wake faulting thread unconditionally on zero/copy ioctls before
returning -EEXIST.
(3) Change the userfaultfd_must_wait() to hold locks.
This patch took the first approach, but the others are valid solutions
with different tradeoffs.
Link: https://lkml.kernel.org/r/20210808020724.1022515-4-namit@vmware.com
Signed-off-by: Nadav Amit <namit@vmware.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
